The invention relates, generally, to pipe handling elevators used for lifting and lowering oilfield tubulars, usually as strings of pipe being tripped into or out of an oil or gas well.
It is well known in the art of drilling, completion and workover of earth boreholes in the oil, gas and geothermal industries to run strings of oilfield tubulars into and out of such boreholes, sometimes referred to as xe2x80x9ctripping inxe2x80x9d or xe2x80x9ctripping outxe2x80x9d. Such tubulars can be, for example, drill pipe, drill collars, casing and tubing. It is also well known to use elevators in such tripping in or out operations to lift or lower such tubulars out of, or into the wells. The handling gear for such tubulars is oftentimes much alike in principle for all sizes but the difference in scale is impressive. Well casing with a diameter of six feet, with a two inch wall thickness, is not uncommon.
Elevators in the prior art typically are hinged, heavy clamps attached to a hook and traveling block by bail-like arms, sometimes referred to simply as xe2x80x9cbailsxe2x80x9d. Such elevators oftentimes use one or more doors which are themselves quite heavy, and which may require two or three strong men to close or hinge the one or two doors around the tubular. Doors are a common feature but there are single door and split door types. One type simply hinges to open to admit or eject pipe. In hoisting a joint of drill pipe, the elevators are latched onto the pipe just below the tool joint (coupling) which prevents the drill pipe from slipping through the elevators. Similarly, in lifting casing or tubing, the sections of such tubulars have either an upset end, i.e., one in which the O.D. is larger than the primary diameter of the casing or tubing, or they are joined together with a collar having an enlarged O.D. In all of these type of operations, the elevator when hinged to the closed position, i.e., when the one or two doors are closed shut, the internal diameter of the elevator is less than the O.D. of the end of the enlarged tool joint, upset, or collar to prevent the tubular from slipping through the elevator.
Handling practices differ between small and rather large diameter pipe. Each section of very large pipe will typically be picked up from the horizontal position and swung to the vertical for stabbing into the connection of the assembled tubular string. Such large pipe, for example, large diameter steel casing, presents special problems. When elevators are placed on the horizontal pipe they have to pivot to orient the elevator throat opening downward. That leaves the doors, on door-type elevators, swinging on hinges. The doors on a large elevator may weigh several hundred pounds. To close such doors, drilling crew men place themselves in hazardous situations. The rigging devised to get the doors closed often is creative, but risky.
An elevator with doors needs clearance for the doors to swing in the closing arc under the pipe being engaged. The pipe has to be elevated, or clearance otherwise provided, for the swinging door.
The elevators discussed above are of the so-called xe2x80x9cnon-slipxe2x80x9d variety. There are other elevators which grasp the tubular and can be used to then hoist or lower the tubular, but the grasping elevators are typically used with the light weight tubulars.
The elevators of the xe2x80x9cnon-slipxe2x80x9d variety have generally been constructed with doors (generally, one or two) which open to allow the insertion or removal of the tubulars. These doors have traditionally been heavy, slow in operation, difficult to handle and present a considerable safety hazard to the operator. Also, the balance point of the elevator will change dramatically when the doors are opened, thus exacerbating handling problems and adding danger to the operator.
Especially with very heavy tubulars, for example, 20xe2x80x3-30xe2x80x3 casing, the tubular is initially in a horizontal position, laying in place, for example, on or near the floor beneath a derrick, and the hinged door elevator is lowered near the point of attachment to the tubular. The derrick hands then are required to open the very heavy door or doors, which may weigh several hundred pounds, to allow the elevator to be placed over the tubular. Moreover, because the door or doors must close around the tubular, the tubular end around which the elevator is placed must be above the derrick floor.
The present invention avoids the above mentioned shortcomings by eliminating the troublesome door members. Retention of the pipe is then accomplished by a system of multiple pipe catches, which are automatically deployed after the insertion of the pipe joint and which automatically retract during insertion of a pipe joint. Importantly, since this elevator lacks swinging doors, the element of the greatest safety concern is eliminated and, the equilibrium of the elevator is undisturbed during insertion or removal of pipe.
When a tubular approaches the elevator, according to the present invention, the tubular first contacts the disconnector arms. As insertion continues, the disconnector arms are swung away in an arc-like path and this motion actuates the disconnector links which disengage the safety latches, allowing the pipe catches freedom to move. The continuing movement of the pipe into the elevator next causes the pipe to contact the pipe catches directly and pushes them out of the way against a nominal spring force. After the pipe is fully seated into the elevator, the pipe catches (no longer restrained by the pipe body) will automatically deploy by means of spring power. The pipe is now mechanically entrapped and cannot fall out of the elevator. As a function of the mechanism""s geometry, the greater the force from the pipe resting against the catches, the greater will be the resistance to opening. The pipe catches, in effect, become self-energizing. In fact, it will not be possible to manually open the elevator if a side force against the catches is present. This feature is an additional safety benefit.
In practicing the methods according to the present invention, elevators can be dropped or lowered onto a horizontal tubular, or swung against a vertical tubular to latch around the tubular, thus by avoiding all or most of the problems associated with using hinged door elevators.
The present invention comprises a horseshoe, or xe2x80x9cUxe2x80x9d shaped body having first and second extending arms separated by a throat to accept a pipe or other tubular. On each arm a blocking member imposes into the passage to and from the throat and either blocking member will prevent pipe (within the elevator rating size) from moving out of the throat of the elevator. The blocking member is spring biased to the blocking, or closed state. In the closed state, a spring biased security lock goes to the locked state, and the blocking member is immobilized in the closed state. There are two ways to free the blocking member. One way is for pipe to be urged toward the throat where it engages an enabling lever which lifts the security lock and frees the blocking member to move to admit pipe to the throat. The second way to manipulate the blocking member is to activate a dumping lever which lifts the security lock and moves further to move the blocking member away from the throat to permit pipe to move out of the throat.
The elevator has no structure that prevents the elevator from engaging pipe lying on a rig floor. The elevator freely pivots within the loops of bails which engage ears, one on each side of the body.
Not all elevators are suspended from the traveling blocks by bails, the term used herein represents any of the many contrivances serving the equivalent function in suspending elevators from traveling blocks or the equivalent hoisting apparatus.
In the preferred embodiment, and as a special feature of the invention, the ears are positioned such that the lift vector, originating at the transverse line about which the ears rotate within the bail loops, passes some distance from the centerline of pipe, when positioned for lifting, within the throat. With an open throat, the periphery of the ledge that engages the lifting surface of the pipe, normally the lower surface of a connector, represents an area that has a geometric center shifted toward the back of the throat. Ideally, but not in a limiting sense, the extended lift vector passes through, or near that geometric center.
These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached claims and appended drawings.